Aesir: The primary "pantheon" or group of Norse gods (led by Odin)
Vanir: The secondary "pantheon" or group of Norse gods (led by Frey)
The two groups warred against each other early in time, but after that lived peacefully.
Snow fell on the four quarters of the world; icy winds blew from every side; the sun and the moon were hidden by storms. It was the Fimbul Winter: no spring came and no summer; no autumn brought harvest or fruit, and winter grew into winter again.
There was three years' winter. The first was called the Winter of Winds: storms blew and snows drove down and frosts were mighty. The children of men could hardly keep alive in that dread winter.
The second winter was called the Winter of the Sword: those who were left alive amongst men robbed and slew for what was left to feed on; brother fell on brother and slew him, and over all the world there were mighty battles.
And the third winter was called the Winter of the Wolf. Then the ancient witch who lived in Jarnvid, the Iron Wood, fed the Wolf Managarm on unburied men and on the corpses of those who fell in battle. Mightily grew and flourished the Wolf that was to be the devourer of Mani, the Moon. The Champions in Valhalla would find their seats splashed with the blood that Managarm dashed from his jaws; this was a sign to the Gods that the time of the last battle was approaching.
A rooster crowed; far down in the bowels of the earth he was and beside Hela's habitation: the rusty-red rooster of Hel crowed, and his crowing made a stir in the lower worlds. In Jötunheim, the realm of the Giants, a rooster crowed, Fialar, the crimson rooster, and at his crowing the Giants aroused themselves. High up in Asgard, the realm of the Gods, a rooster crew, the golden rooster Gullinkambir, and at his crowing the Champions in Valhalla bestirred themselves.
A dog barked; deep down in the earth a dog barked; it was Garm, the hound with bloody mouth, barking in Gnipa's Cave. The Dwarfs who heard groaned before their doors of stone. The tree Ygdrassil moaned in all its branches. There was a rending noise as the Giants moved their ship; there was a trampling sound as the hosts of Muspelheim, the Land of Fire, gathered their horses.
But Jötunheim and Muspelheim and Hel waited tremblingly; it might be that Fenrir the Wolf might not burst the bonds wherewith the Gods had bound him. Without his being loosed the Gods might not be destroyed. And then was heard the rending of the rock as Fenrir broke loose. For the second time the Hound Garm barked in Gnipa's Cave.
Then was heard the galloping of the horses of the riders of Muspelheim; then was heard the laughter of Loki, the Betrayer; then was heard the blowing of Heimdall's horn; then was heard the opening of Valhalla's five hundred and forty doors, as eight hundred Champions made ready to pass through each door.
Odin took council with Mimir's head. Up from the waters of the Well of Wisdom he drew it, and by the power of the runes he knew he made the head speak to him. Where best might the Æsir and the Vanir and the Einherjar, who were the Champions of Midgard, meet, and how best might they fight against the forces of Muspelheim and Jötunheim and Hel? The head of Mimir counseled Odin to meet them on Vigard Plain and to wage there such war that the powers of evil would be destroyed forever, even though his own world should be destroyed with them.
The riders of Muspelheim reached Bifröst, the Rainbow Bridge prepared to storm the City of the Gods and fill it with flame. But Bifröst broke under the weight of the riders of Muspelheim, and they came not to the City of the Gods.
Jörmungand, the serpent that encircles the world, reared itself up from the sea. The waters flooded the lands, and the remnant of the world's inhabitants was swept away. That mighty flood floated Naglfar, the Ship of Nails that the Giants were so long building, and floated the ship of Hel also. With Hrymer the Giant steering it, Naglfar sailed against the Gods, with all the powers of Jötunheim aboard. And Loki steered the ship of Hel with the Wolf Fenrir upon it for the place of the last battle.
Since Bifröst was broken, the Æsir and the Vanir, the Einherjer and the Valkyries rode downward to Vigard through the waters of the roaring River. Odin rode at the head of his Champions. His helmet was of gold and in his hand was his spear Gungnir. Thor, with his mighty hammer Mjölnir, and Tyr, the great warrior of the Gods, were in his company.
In Mirkvid, the Dark Forest, the Vanir stood against the host of Muspelheim, the land of fire. From the broken end of the Rainbow Bridge the riders of Muspelheim came, all flashing and flaming, with fire before them and after them. The Vanir, Njörd was there with Skadi, his Giant wife, fierce in her war-dress; Freya was there also, and Frey had Gerda beside him as a battle-maiden. Terribly bright flashed Surtur's sword. Frey, the leader of the Vanir fought against Surtur of the Muspelheim but Frey no longer had his magic sword -- he had given it up to win the hand of his wife Gerda -- and he was defeated by Surtur and perished.
And now, for the third time, Garm, the hound with blood upon his jaws, barked. He had broken loose on the world, and with fierce bounds he rushed toward Vigard Plain, where the Gods had assembled their powers. Loud barked Garm. The Eagle Hræsvelgur screamed on the edge of heaven. Then the skies split, and the tree Ygdrassil was shaken in all its roots.
To the place where the Gods had drawn up their ranks came the ship of Jötunheim and the ship of Hel -- came the riders of Muspelheim, and Garm, the hound with blood upon his jaws. And out of the sea that now surrounded the plain of Vigard the serpent Jörmungand came. All the forces of evil gathered against the Einherjar -- those champions of Midgard, the realm of Men -- those brave warriors that Odin's valkyries had gathered to Valhalla. On the plain of Vigard, evil rose against the Æsir and the Vanir and the Einherjar.
What said Odin to the Gods and to the Champions who surrounded him?
"We will give our lives and let our world be destroyed, but we will battle so that these evil powers will not live after us."
Out of Hel's ship sprang Fenrir the Wolf. His mouth gaped; his lower jaw hung against the earth, and his upper jaw scraped the sky. Against the Wolf Odin All-Father fought. Thor could not aid him, for Thor was locked in battle against Jörmungand, the monstrous serpent.
In a great battle, Fenrir the Wolf killed Odin All-Father. But the younger Gods were now advancing to the battle; and Vidar, the Silent God, came face to face with Fenrir. He laid his foot on the Wolf's lower jaw and with his hands he seized the upper jaw and tore his gullet. Thus died Fenrir, the fiercest of all the enemies of the Gods.
Jörmungand, the monstrous serpent, would have overwhelmed all with the venom he was ready to pour forth. But Thor sprang forward and crushed him with a stroke of his hammer Mjölnir. Then Thor stepped back nine paces. But the serpent blew his venom over him. Blinded and choked and burnt Thor, the World's Defender, perished.
Loki sprang from his ship and strove with Heimdall, the Warder of the Rainbow Bridge and the Watcher for the Gods. Loki and Heimdall -- evenly matched -- killed each other with mighty blows.
Little Hnossa, the youngest of all the Dwellers in Asgard, ignoring the battles raging around her, knelt down next to Heimdall who had been her friend. With gentle hands, Little Hnossa closed Heimdall's eyes -- eyes that would never again look across time and space -- and mourned him.
No one mourned the death of Loki the Betrayer.
Bravely fought Tyr, the great warrior of the Gods, who had sacrificed his right hand, his swordhand, for the binding of the Wolf Fenrir. Bravely he fought, and many of the powers of evil perished by his strong left hand. But Garm, the hound with bloody jaws, slew Tyr.
And now the riders of Muspelheim, the Land of fire, came down on the field. Bright and gleaming were all their weapons. Before them and behind them went wasting fires. Surtur cast flame upon the earth; the tree Ygdrassil took fire and burned in all its great branches; the World Tree was wasted in the blaze. But the fearful fire that Surtur brought on the earth also destroyed him and all his host.
The Wolf Hati caught up on Sol, the Sun; the Wolf Managarm seized on Mani, the Moon; they devoured them; stars fell, and darkness came down on the world.
The seas flowed over the burnt and wasted earth and the skies were dark above the sea, for Sol and Mani were no more. But at last the seas drew back and earth appeared again, green and beautiful. A new Sun and a new Moon appeared in the heavens, one a daughter of Sol and the other a daughter of Mani.
Four of the younger Gods stood on the highest of the world's peaks; they were Vidar and Vali, the sons of Odin, and Modi and Magni, the sons of Thor. Modi and Magni found Mjölnir, Thor's hammer, and with it they slew the monsters that still raged through the world, the Hound Garm and the Wolf Managarm.
Vidar and Vali found in the grass the golden tablets on which were inscribed the runes of wisdom of the elder Gods. The runes told them of a heaven that was above Asgard, of the golden tower, Gimlé, that was untouched by Surtur's fire -- the golden tower where righteous men go when they die.
Baldur and Hödur came from Hela's habitation, and the last Gods sat on the peak together and spoke with each other, remembering the secrets and the happenings they had known before Ragnarök, the Twilight of the Gods.
Deep in a wood two of human kind were left; the flames of Surtur did not touch them; they slept, and when they wakened the world was green and beautiful again. These two fed on the dews of the morning; a woman and a man they were, Lif and Lifthrasir. They walked abroad in the world, and from them and from their children came the men and women who spread themselves over the earth.